Dynamic stabilization connecting member with pre-tensioned solid core

ABSTRACT

A dynamic longitudinal connecting member assembly includes an anchor member having an integral or otherwise fixed elongate core of circular or non-circular cross-section. The core is pre-tensioned and extends through at least one elastic spacer and at least one outer sleeve. The anchor member and the outer sleeve each attach to at least one bone anchor. In operation, the core is held in tension by the spacer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/459,492, filed Jul. 1, 2009, which is a continuation-in-part of U.S.application Ser. No. 12/156,260, filed May 30, 2008 that claimed thebenefit of U.S. Provisional Application No. 60/932,567 filed May 31,2007, all of which are incorporated by reference herein. U.S.application Ser. No. 12/156,260 also claimed the benefit of U.S.Provisional Application No. 60/994,068 filed Sep. 17, 2007, which isincorporated by reference herein. U.S. application Ser. No. 12/459,492also claimed the benefit of U.S. Provisional Patent Application Ser. No.61/134,480, filed Jul. 10, 2008 and claimed the benefit of U.S.Provisional Patent Application Ser. No. 61/137,743, filed Aug. 1, 2008.U.S. application Ser. No. 12/459,492 was also a continuation-in-part ofU.S. patent application Ser. No. 12/148,465, filed Apr. 18, 2008 thatclaimed the benefit of U.S. Provisional Patent Application Ser. No.60/927,111, filed May 1, 2007, all of which are incorporation byreference herein.

BACKGROUND OF THE INVENTION

The present invention is directed to dynamic fixation assemblies for usein bone surgery, particularly spinal surgery, and in particular tolongitudinal connecting members for such assemblies, the connectingmembers being attached to at least two bone fasteners.

Historically, it has been common to fuse adjacent vertebrae that areplaced in fixed relation by the installation therealong of bone screwsor other bone anchors and cooperating longitudinal connecting members orother elongate members. Fusion results in the permanent immobilizationof one or more of the intervertebral joints. Because the anchoring ofbone screws, hooks and other types of anchors directly to a vertebra canresult in significant forces being placed on the vertebra, and suchforces may ultimately result in the loosening of the bone screw or otheranchor from the vertebra, fusion allows for the growth and developmentof a bone counterpart to the longitudinal connecting member that canmaintain the spine in the desired position even if the implantsultimately fail or are removed. Because fusion has been a desiredcomponent of spinal stabilization procedures, longitudinal connectingmembers have been designed that are of a material, size and shape tolargely resist flexure, extension, torsion, distraction and compression,and thus substantially immobilize the portion of the spine that is to befused. Thus, longitudinal connecting members are typically uniform alongan entire length thereof, and usually made from a single or integralpiece of material having a uniform diameter or width of a size toprovide substantially rigid support in all planes.

An alternative to fusion, which immobilizes at least a portion of thespine, and the use of more rigid longitudinal connecting members orother rigid structure has been a “soft” or “dynamic” stabilizationapproach in which a flexible loop-, S-, C- or U-shaped member or acoil-like and/or a spring-like member is utilized as an elasticlongitudinal connecting member fixed between a pair of pedicle screws inan attempt to create, as much as possible, a normal loading patternbetween the vertebrae in flexion, extension, distraction, compression,side bending and torsion. Another type of soft or dynamic system knownin the art includes bone anchors connected by flexible cords or strands,typically made from a plastic material. Such a cord or strand may bethreaded through cannulated spacers that are disposed between adjacentbone anchors when such a cord or strand is implanted, tensioned andattached to the bone anchors. The spacers typically span the distancebetween bone anchors, providing limits on the bending movement of thecord or strand and thus strengthening and supporting the overall system.Such cord or strand-type systems require specialized bone anchors andtooling for tensioning and holding the cord or strand in the boneanchors. Although flexible, the cords or strands utilized in suchsystems do not allow for elastic distraction of the system onceimplanted because the cord or strand must be stretched or pulled tomaximum tension in order to provide a stable, supportive system.

The complex dynamic conditions associated with spinal movement createchallenges for the design of elongate elastic longitudinal connectingmembers that exhibit an adequate fatigue strength to providestabilization and protected motion of the spine, without fusion, andthat allow for some natural movement of the portion of the spine beingreinforced and supported by the elongate elastic or flexible connectingmember. A further challenge are situations in which a portion or lengthof the spine requires a more rigid stabilization, possibly includingfusion, while another portion or length may be better supported by amore dynamic system that allows for protective movement.

SUMMARY OF THE INVENTION

Longitudinal connecting member assemblies according to the invention foruse between at least two bone attachment structures or anchors providedynamic, protected motion of the spine. A longitudinal connecting memberassembly according to the invention has an inner pre-tensioned core ofcircular or non-circular cross-section that is integral or otherwisefixed to a first bone anchor attachment portion. At least one elasticspacer surrounds the core and is slidable along the core at a locationbetween a pair of adjacent bone anchors. At least one outer sleeve alsosurrounds the core and is in sliding relationship with the core. Theouter sleeve also engages at least one bone anchor. The inner core andouter elastic spacer cooperate dynamically, with the outer sleeve beingin compression while the core is in tension. The assembly may furtherinclude an elastic end bumper that also is in compression and placesdistractive force on the core.

In one embodiment, an improved medical implant assembly having at leasttwo bone anchor attachment structures cooperating with a longitudinalconnecting member is provided, including an anchor member portion thatis in engagement with one of the at least two bone anchor attachmentstructures, at least one compressible outer spacer, and at least onesleeve. The anchor member portion has a pre-tensioned member portion ofreduced diameter that extends from an end thereof. The pre-tensionedmember portion is received in the spacer, and the spacer is positionedbetween the at least two bone anchor attachment structures. Thepre-tensioned member portion is also received within the sleeve and inslidable relationship therewith. The sleeve is in engagement with theother of the at least two bone anchor attachment structures. Theimprovement may further include an elastic bumper that engages thesleeve and receives the pre-tensioned member portion therein. Theimprovement may further include a fixation structure that is secured tothe pre-tensioned member portion at an end thereof opposite the anchormember portion.

In another embodiment, an improved medical implant assembly having atleast two bone attachment structures cooperating with a longitudinalconnecting member is provided, the improvement wherein the longitudinalconnecting member includes an anchor member portion in engagement withone of the at least two bone attachment structures, the anchor memberportion having a pre-tensioned bendable core extension of reduceddiameter along a length thereof, the core extension attached to andextending from the anchor member portion and having a linear and anon-linear configuration; at least one compressible outer spacer, thecore extension being received in the spacer, the spacer being positionedbetween the at least two bone attachment structures; and at least onesleeve, the core extension being received within the sleeve and inslidable relationship therewith, the sleeve being in engagement with theother of the at least two bone attachment structures.

In yet another embodiment, an improved medical implant assembly havingat least two bone anchor attachment structures cooperating with alongitudinal connecting member is provided, the improvement wherein thelongitudinal connecting member includes an anchor member portion inengagement with one of the at least two bone anchor attachmentstructures, the anchor member portion having a pre-tensioned memberportion of reduced diameter extending from an end thereof; at least onecompressible outer spacer, the pre-tensioned member portion beingreceived in the spacer, the spacer being positioned between the at leasttwo bone anchor attachment structures; and at least one sleeve, thepre-tensioned member portion being received within the sleeve and inslidable relationship therewith, the sleeve being in engagement with theother of the at least two bone anchor attachment structures. In someembodiments, the longitudinal connecting member also includes one ormore of an elastic bumper and a fixation structure. Further, thepre-tensioned member portion is fixed to the anchor member portion at anend thereof, in some embodiments.

In still another embodiment, a medical implant assembly having at leasttwo bone attachment structures cooperating with a longitudinalconnecting member is provided, the improvement wherein the longitudinalconnecting member includes an anchor member portion in engagement withone of the at least two bone attachment structures, the anchor memberportion having a pre-tensioned bendable core extension of reduceddiameter along a length thereof, the core extension attached to andextending from the anchor member portion and having a linear and anon-linear configuration; at least one compressible outer spacer, thecore extension being received in the spacer, the spacer being positionedbetween the at least two bone attachment structures; and at least onesleeve, the core extension being received within the sleeve and inslidable relationship therewith, the sleeve being in engagement with theother of the at least two bone attachment structures.

In another embodiment, a medical implant assembly is provided, theassembly including a longitudinal connecting member having a stiffportion secured to at least a first bone attachment structure, the stiffportion being coaxial with a less stiff core extension portion ofreduced width relative to the stiff portion, the core extension being inslidable relation with at least a second end bone attachment structure;at least one solid non-slitted outer spacer positioned entirely outsideof the core extension and between the at least first and second end boneattachment structures, the spacer being in slidable relation with thecore extension; and at least one end fixing structure and at least oneelastic bumper, both the end fixing structure and the elastic bumperbeing positioned entirely outside of the at least second end boneattachment structure, wherein the bumper is positioned around the coreextension and between the fixing structure and the at least second endbone attachment structure, and wherein the bumper is in slidablerelation with the core extension; and wherein the fixing structure isslidable on the core section, compressible against the bumper andsecurable to the core extension.

In a further embodiment, the core extension is in tension. In somefurther embodiments, the core extension is maintained in tension byaxial elastic distraction from the bumper. In some further embodiments,the core extension is made of at least one of a polymer, PEEK and anon-metal. In some further embodiments, at least one sleeve ispositioned around and between the core extension and the bone attachmentstructure, the sleeve being secured to at least the bone attachmentstructure. In some further embodiments, the tensioned core extension isadapted to provide resilient bending stiffness for the longitudinalconnecting member while cooperating with the bone attachment structures.In some further embodiments, the end fixing structure is positionedentirely outside of the bumper. In some further embodiments, the bumperand the spacer are positioned entirely outside of the sleeve.

Objects and Advantages of the Invention

An object of the invention is to provide dynamic medical implantstabilization assemblies having longitudinal connecting members thatinclude a pre-tensioned inner core that allows for some bending,torsion, compression and distraction of the assembly. Another object ofthe invention is to provide such an assembly including an elasticpre-compressed outer spacer or sleeve. A further object of the inventionis to provide dynamic medical implant longitudinal connecting membersthat may be utilized with a variety of bone screws, hooks and other boneanchors. Additionally, it is an object of the invention to provide alightweight, reduced volume, low profile assembly including at least twobone anchors and a longitudinal connecting member therebetween.Furthermore, it is an object of the invention to provide apparatus andmethods that are easy to use and especially adapted for the intended usethereof and wherein the apparatus are comparatively inexpensive to makeand suitable for use.

Other objects and advantages of this invention will become apparent fromthe following description taken in conjunction with the accompanyingdrawings wherein are set forth, by way of illustration and example,certain embodiments of this invention.

The drawings constitute a part of this specification and includeexemplary embodiments of the present invention and illustrate variousobjects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged front elevational view of a dynamic fixationconnecting member assembly according to the invention including ananchor member integral with an inner core, two elastic spacers, twosleeves, an elastic bumper and a crimping ring.

FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. 1.

FIG. 3 is an enlarged perspective view of the anchor member of FIG. 1.

FIG. 4 is an enlarged perspective view of one of the sleeves of FIG. 1.

FIG. 5 is an enlarged perspective view of another of the sleeves of FIG.1.

FIG. 6 is an enlarged exploded front elevational view of the assembly ofFIG. 1.

FIG. 7 is an enlarged perspective view of the crimping ring of FIG. 1.

FIG. 8 is an enlarged perspective view of the elastic bumper of FIG. 1.

FIG. 9 is an enlarged front perspective view of an elastic spacer ofFIG. 1.

FIG. 10 is an enlarged rear perspective view of the elastic spacer ofFIG. 9.

FIG. 11 is an enlarged front perspective view of another elastic spacerof FIG. 1.

FIG. 12 is an enlarged rear perspective view of the elastic spacer ofFIG. 11.

FIG. 13 is a reduced front elevational view of the assembly of FIG. 1shown with three cooperating bone screws.

FIG. 14 is an enlarged front elevational view of a second embodiment ofa dynamic fixation connecting member assembly according to the inventionincluding an anchor member integral with an inner core, an elasticspacer, a sleeve, an elastic bumper and a crimping ring.

FIG. 15 is a reduced exploded front elevational view of the assembly ofFIG. 14.

FIG. 16 is a cross-sectional view taken along the line 16-16 of FIG. 14.

FIG. 17 is a reduced front elevational view of the assembly of FIG. 14shown with three cooperating bone screws.

FIG. 18 is front elevational view of a third embodiment of a dynamicfixation connecting member assembly according to the invention shownwith four cooperating bone screws.

FIG. 19 is a front elevational view of a fourth embodiment of a dynamicfixation connecting member assembly according to the invention withportions broken away to show the detail thereof.

FIG. 20 is a front elevational view of a fifth embodiment of a dynamicfixation connecting member assembly according to the invention with aninner threaded core shown in phantom.

FIG. 21 is a front elevational view of a sixth embodiment of a dynamicfixation connecting member assembly according to the invention.

FIG. 22 is a reduced exploded front elevational view of the connectingmember of FIG. 21.

FIG. 23 is a reduced cross-sectional view taken along the line 23-23 ofFIG. 21.

FIG. 24 is a front elevational view of a seventh embodiment of a dynamicfixation connecting member assembly according to the invention shownwith three bone screws.

FIG. 25 is an enlarged perspective view of an eighth embodiment of adynamic fixation connecting member assembly according to the inventionincluding an anchor member integral with an inner core, an elasticspacer, a sleeve, an elastic bumper and a crimping member.

FIG. 26 is a cross-sectional view taken along the line 26-26 of FIG. 25.

FIG. 27 is an enlarged exploded front elevational view of the assemblyof FIG. 25.

FIG. 28 is an enlarged perspective view of the anchor member of FIG. 25.

FIG. 29 is an enlarged side elevational view of the anchor member ofFIG. 25.

FIG. 30 is an enlarged perspective view of the spacer of FIG. 25.

FIG. 31 is an enlarged side elevational view of the spacer of FIG. 25.

FIG. 32 is an enlarged perspective view of the sleeve of FIG. 25.

FIG. 33 is an enlarged side elevational view of the sleeve of FIG. 25.

FIG. 34 is an enlarged perspective view of the elastic bumper of FIG.25.

FIG. 35 is an enlarged side elevational view of the elastic bumper ofFIG. 25.

FIG. 36 is an enlarged perspective view of the crimping member of FIG.25.

FIG. 37 is an enlarged side elevational view of the crimping member ofFIG. 25.

FIG. 38 is an enlarged front elevational view of the assembly of FIG. 25shown with two cooperating bone screws with portions broken away to showthe detail thereof.

FIG. 39 is an enlarged perspective view of a ninth embodiment of adynamic fixation connecting member assembly according to the inventionincluding an anchor member integral with an inner core, an elasticspacer with a trapezoidal face, a sleeve, an elastic bumper and acrimping member.

FIG. 40 is a reduced exploded perspective view of the assembly of FIG.39.

FIG. 41 is an enlarged front elevational view of the elastic spacer ofFIG. 39.

FIG. 42 is an enlarged side elevational view of the elastic spacer ofFIG. 39.

FIG. 43 is an enlarged and partial front elevational view of theassembly of FIG. 39 shown cooperating with a pair of bone screws.

FIG. 44 is an enlarged and partial front elevational view similar toFIG. 43 showing the assembly in a loaded condition.

FIG. 45 is an enlarged front elevational view of a tenth embodiment of adynamic fixation connecting member assembly according to the inventionincluding an anchor member integral with an inner core, a first elasticspacer with a trapezoidal face, a first sleeve, a second elastic spacer,a second sleeve, an elastic bumper and a crimping member.

FIG. 46 is an enlarged front elevational view similar to FIG. 45 withportions broken away to show the detail thereof.

FIG. 47 is an enlarged perspective view of the first sleeve of FIG. 45.

FIG. 48 is an enlarged and partial perspective view of the assembly ofFIG. 45 shown cooperating with three bone screws and with portionsbroken away to show the detail thereof.

FIG. 49 is an enlarged and partial perspective view similar to FIG. 48showing the assembly of FIG. 45 under a load.

FIG. 50 is an enlarged perspective view of an eleventh embodiment of adynamic fixation connecting member assembly according to the inventionincluding an anchor member integral with an inner core, a first elasticspacer with a trapezoidal face, a first sleeve, a second elastic spacerwith a trapezoidal face, a second sleeve, an elastic bumper and acrimping member.

FIG. 51 is a reduced and partial front elevational view of the assemblyof FIG. 50 shown cooperating with three bone screws.

FIG. 52 is a partial front elevational view similar to FIG. 51 showingthe assembly of FIG. 50 under a load.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure. It is also noted that any reference tothe words top, bottom, up and down, and the like, in this applicationrefers to the alignment shown in the various drawings, as well as thenormal connotations applied to such devices, and is not intended torestrict positioning of the connecting member assemblies of theapplication and cooperating bone anchors in actual use.

With reference to FIGS. 1-13, the reference numeral 1 generallydesignates a non-fusion dynamic stabilization longitudinal connectingmember assembly according to the present invention. The connectingmember assembly 1 includes an anchor member, generally 4, having anelongate segment or inner core 6 and a bone anchor attachment portion 8;a first elastic spacer 10; a first sleeve 12; a second elastic spacer14; a second sleeve 16; an elastic bumper 18; and a crimping ring 20;all substantially symmetrically aligned with respect to a central axis Aof the anchor member 4. The elongate core 6 of the anchor member 4 isreceivable within the spacer 10, the first sleeve 12, the second spacer14, the second sleeve 16, the bumper 18 and the crimping ring 20. Thus,the axis A of the anchor member 4 is also the axis of the fullyassembled assembly 1. As will be described in greater detail below, whenfully assembled and fixed with all components fixed in position as shownin FIG. 1, the inner core 6 is in tension and the spacers 10 and 14 andthe bumper 18 are in compression.

As illustrated in FIG. 13, the dynamic connecting member assembly 1cooperates with at least three bone anchors, such as the polyaxial bonescrews, generally 25 and cooperating closure structures 27, the assembly1 being captured and fixed in place at the anchor portion 8, the sleeve12 and the sleeve 16 by cooperation between the bone screws 25 and theclosure structures 27. Because the anchor portion 8 and the sleeves 12and 16 have substantially solid cylindrical surfaces, the connectingmember assembly 1 may be used with a wide variety of bone screws andother bone anchors already available for cooperation with more rigidrods including fixed, monoaxial bone screws, hinged bone screws,polyaxial bone screws, and bone hooks and the like, with or withoutcompression inserts, that may in turn cooperate with a variety ofclosure structures having threads, flanges, or other structure forfixing the closure structure to the bone anchor, and may include otherfeatures, for example, external or internal drives, break-off tops andinner set screws. The bone anchors, closure structures and theconnecting member assembly 1 are then operably incorporated in anoverall spinal implant system for correcting degenerative conditions,deformities, injuries, or defects to the spinal column of a patient.

The illustrated polyaxial bone screws 25 each include a shank 30 forinsertion into a vertebra (not shown), the shank 30 being pivotallyattached to an open receiver or head 31. The shank 30 includes athreaded outer surface and may further include a central cannula orthrough-bore disposed along an axis of rotation of the shank. Thethrough bore provides a passage through the shank interior for a lengthof wire or pin inserted into the vertebra prior to the insertion of theshank 30, the wire or pin providing a guide for insertion of the shank30 into the vertebra. The receiver 31 includes a pair of spaced andgenerally parallel arms that form an open generally U-shaped channeltherebetween that is open at distal ends of such arms. The receiver armseach include radially inward or interior surfaces that have adiscontinuous guide and advancement structure mateable with cooperatingstructure on the closure structure 27. The guide and advancementstructure may be a partial helically wound flangeform configured to mateunder rotation with a similar structure on the closure structure 27 or abuttress thread, a square thread, a reverse angle thread or other threadlike or non-thread like helically wound advancement structures foroperably guiding under rotation and advancing the closure structure 27downward between the receiver arms and having such a nature as to resistsplaying of the receiver arms when the closure 27 is advanced betweenthe receiver arms.

The shank 30 and the receiver 31 may be attached in a variety of ways.For example, a spline capture connection as described in U.S. Pat. No.6,716,214, and incorporated by reference herein, may be used wherein thebone screw shank includes a capture structure mateable with a retainingstructure disposed within the receiver. The retaining structure includesa partially spherical surface that is slidingly mateable with acooperating inner surface of the receiver 31, allowing for a wide rangeof pivotal movement between the shank 30 and the receiver 31. Polyaxialbone screws with other types of capture connections may also be usedaccording to the invention, including but not limited to, threadedconnections, frictional connections utilizing frusto-conical orpolyhedral capture structures, integral top or downloadable shanks, andthe like. Also, as indicated above, polyaxial and other bone screws foruse with connecting members of the invention may have bone screw shanksthat attach directly to the connecting member or may include compressionmembers or inserts that engage the bone screw shank and cooperate withthe shank, the receiver and the closure structure to secure theconnecting member assembly to the bone screw and/or fix the bone screwshank at a desired angle with respect to the bone screw receiver thatholds the longitudinal connecting member assembly. Furthermore, althoughthe closure structure 27 of the present invention is illustrated withthe polyaxial bone screw 25 having an open receiver or head 31, itforeseen that a variety of closure structure may be used in conjunctionwith any type of medical implant having an open or closed head orreceiver, including monoaxial bone screws, hinged bone screws, hooks andthe like used in spinal surgery.

To provide a biologically active interface with the bone, the threadedshank 30 may be coated, perforated, made porous or otherwise treated.The treatment may include, but is not limited to a plasma spray coatingor other type of coating of a metal or, for example, a calciumphosphate; or a roughening, perforation or indentation in the shanksurface, such as by sputtering, sand blasting or acid etching, thatallows for bony ingrowth or ongrowth. Certain metal coatings act as ascaffold for bone ingrowth. Bio-ceramic calcium phosphate coatingsinclude, but are not limited to: alpha-tri-calcium phosphate andbeta-tri-calcium phosphate (Ca₃(PO₄)₂, tetra-calcium phosphate(Ca₄P₂O₉), amorphous calcium phosphate and hydroxyapatite(Ca₁₀(PO₄)₆(OH)₂). Coating with hydroxyapatite, for example, isdesirable as hydroxyapatite is chemically similar to bone with respectto mineral content and has been identified as being bioactive and thusnot only supportive of bone ingrowth, but actively taking part in bonebonding.

With reference to FIG. 13, the closure structure 27 can be any of avariety of different types of closure structures for use in conjunctionwith the present invention with suitable mating structure on theinterior surface of the upstanding arms of the receiver 31. Theillustrated closure structure 27 is rotatable between the spaced arms,but could be a slide-in closure structure. The illustrated closurestructure 27 is substantially cylindrical and includes an outerhelically wound guide and advancement structure in the form of a flangeform that may take a variety of forms, including those described inApplicant's U.S. Pat. No. 6,726,689, which is incorporated herein byreference. It is also foreseen that according to the invention theclosure structure guide and advancement structure could alternatively bea buttress thread, a square thread, a reverse angle thread or otherthread like or non-thread like helically wound advancement structure foroperably guiding under rotation and advancing the closure structure 27downward between the receiver arms and having such a nature as to resistsplaying of the arms when the closure structure 27 is advanced into theU-shaped channel formed by the arms. The illustrated closure 27 furtherincludes an inner set screw with an internal drive in the form of anaperture utilized for assembly of the set screw and removal of theentire closure 27. It is foreseen that the closure structure 27 mayalternatively include an external drive, such as a break-off headdesigned to allow such a head to break from a base of the closure at apreselected torque, for example, 70 to 140 inch pounds. Such a closurestructure would also include a base having an internal drive to be usedfor closure removal.

Returning to the longitudinal connecting member assembly 1 illustratedin FIGS. 1-13, the assembly 1 is elongate, with the inner core 6 being asubstantially solid, smooth and uniform cylinder or rod having an outercylindrical surface 36 and a substantially circular cross-section. Thecore 6 and integral anchor attachment portion 8 may be made from metal,metal alloys or other suitable materials, including plastic polymerssuch as polyetheretherketone (PEEK), ultra-high-molecularweight-polyethylene (UHMWP), polyurethanes and composites, includingcomposites containing carbon fiber. It is noted that although an anchormember 4 is illustrated in which the components 6 and 8 are integral,the core 6 and the anchor attachment portion 8 may be made fromdifferent materials, for example, the core 6 may be made out of PEEK andfixed or adhered to a bone anchor attachment portion 8 made out oftitanium. The core 6 and attachment portion 8 may include a smallcentral lumen or through-bore (not shown) extending along the centralaxis A. Such a lumen may be used as a passage through the entireassembly 1 interior for a length of a guide wire for aiding insertion ofthe assembly 1 between implanted bone screws 25 in a percutaneous orless invasive procedure.

With particular reference to FIG. 3, the anchor member 4 issubstantially cylindrical along an entire length thereof along the axisA and includes at least two or more circular cross-sections along thelength thereof. The illustrated member 4 includes the slender and thusmore flexible core 6 of a first circular cross-section and the boneanchor attachment portion 8 that has a second circular cross-sectionthat is larger than the core 6 cross-section and thus is more rigid thanthe core 6. The core 6 terminates at an end 38. Prior to final assembly,the core 6 is typically of a length greater than that shown in thedrawing figures so that the core 6 may be grasped by a tool (not shown)near the end 38 and pulled along the axis A in a direction away from theanchor attachment portion 8 in order to place tension on the core 6 aswill be described in greater detail below.

With particular reference to FIGS. 2-3, between the core 6 and theportion 8 is a buttress plate 40 that has a third circular cross-sectionthat is larger than the attachment portion 8 cross-section. The buttressplate 40 is integral with and disposed between the core 6 and theportion 8. Although the illustrated anchor member 4 is substantiallycylindrical, it is foreseen that the core 6, the portion 8 and the plate40 may have other forms, including but not limited to oval, square andrectangular cross-sections as well as other curved or polygonal shapes.The bone anchor attachment portion 8 is of a length along the axis A forcooperating with at least one and up to a plurality of bone attachmentmembers, such as the bone screws 25, hooks or other types of boneanchors. The portion 8 is substantially solid and rigid, with an outercylindrical surface 39 that terminates at an end 41. The plate 40includes a first substantially flat and annular face 42 facing away fromthe core 6 and an opposed parallel substantially flat face 44 facingtoward the core 6. The faces 42 and 44 are disposed substantiallyperpendicular to the axis A. An outer cylindrical surface 46 extendsbetween the faces 42 and 44. A gently sloping transition surface orflange 48 bridges between and connects the outer cylindrical surface 36of the core 6 with the substantially flat face 44 of the buttress plate40.

With particular reference to FIGS. 4 and 5, the sleeves 12 and 16 areeach sized and shaped to be slidingly received over the core 6 along theaxis A and each have a length measured along the axis A that issufficient for the attachment of at least one bone screw 25 thereon.Similar to the anchor member 4, the sleeves 12 and 16 may be made frommetal, metal alloys or other suitable materials, including plasticpolymers such as polyetheretherketone (PEEK), ultra-high-molecularweight-polyethylene (UHMWP), polyurethanes and composites, includingcomposites containing carbon fiber. The sleeves 12 and 16 may be made ofthe same material as the cooperating core 6, for example, the anchormember 4 and the sleeves 12 and 16 may all be made from PEEK; or, forexample, the core 6 may be made from one material, such as PEEK, whilethe sleeves 12 and 16 may be made from another material, such as a metal(e.g. stainless steel or titanium). In order to have low or no weardebris, the sleeve 12 and 16 inner surfaces and/or cooperating core 6outer surfaces may be coated with an ultra thin, ultra hard, ultra slickand ultra smooth coating, such as may be obtained from ion bondingtechniques and/or other gas or chemical treatments.

The illustrated sleeves 12 and 16 each are substantially cylindrical,having outer cylindrical bone anchor attachment surfaces 50 and 52,respectively, that are each of substantially the same diameter as theouter surface 39 of the bone anchor attachment portion 8. Each of thesleeves 12 and 16 further include an inner cylindrical surface 54 and56, respectively, that define a through-bore for the passage of the core6 therethrough. The sleeve 12 includes a pair of integral, opposed endplates 58 and 60 while the sleeve 16 includes a single end plate 62. Theillustrated plates 58, 60 and 62 have outer cylindrical surfaces 64, 66and 68, respectively, that are of substantially the same diameter as thebuttress plate outer cylindrical surface 46. The plates 58 and 60terminate at outer planar and annular surfaces 70 and 72, respectively.The plate 62 terminates at an outer planar and annular surface 74. Thecylindrical surface 52 of the sleeve 16 terminates at an outer planarand annular surface 76.

With reference to FIGS. 8-12, the elastic spacers 10 and 14 and theelastic bumper 18 are sized and shaped to be slidingly received over thecore 6 and may be made from a variety of elastic materials, including,but not limited to natural or synthetic elastomers such as polyisoprene(natural rubber), and synthetic polymers, copolymers, and thermoplasticelastomers, for example, polyurethane elastomers such aspolycarbonate-urethane elastomers. In order to have low or no weardebris, the spacers 10 and 14 and bumper 18 inner and side surfaces mayalso be coated with an ultra thin, ultra hard, ultra slick and ultrasmooth coating, such as may be obtained from ion bonding techniquesand/or other gas or chemical treatments.

The illustrated spacers 10 and 14 advantageously cooperate with the core6 of the anchor member 4, providing limitation and protection ofmovement of the core 6 located between bone screws 25. With particularreference to FIGS. 9-12, the illustrated spacers 10 and 14 are almostidentical, differing only with regard to inner surfaces that definethrough bores for receiving the anchor member core 6. Each of thespacers 10 and 14 have an external substantially cylindrical outersurface 78 and 80, respectively, and internal surfaces 82 and 84,respectively, defining through bores. The internal surface 82 is furtherdefined by a flared or conical outwardly extending surface 86 sized andshaped for cooperating with the surface 48 of the anchor member 4. Thespacer 10 includes opposed substantially planar and annular end surfaces88 and 89 and the spacer 14 includes opposed substantially planar andannular end surfaces 90 and 91. When cooperating with the core 6, theend surfaces 88 and 89 and 90 and 91 are substantially perpendicular tothe axis A. It is foreseen that in some embodiments, the spacers 10 and14 may be of circular, square, rectangular or other cross-sectionincluding curved or polygonal shapes. In the illustrated embodiment,both the spacers 10 and 14 further includes a compression groove 93 and94, respectively. Spacers according to the invention may include one,none or any desired number of grooves that allow for some additionalcompression of the spacers 10 and 14 when pressed upon in an axialdirection by the plates 40, 58, 60 and 62. The illustrated grooves 93and 94 are substantially uniform and circular in cross-section, beingformed in the respective external surfaces 78 and 80 and extendingradially toward respective internal surfaces 82 and 84. The size of theinternal surfaces 82 and 84 allow for some axially directed slidingmovement of the respective spacers 10 and 14 with respect to the coresurface 36.

The core 6 and cooperating compressible spacers 10 and 14 allows forsome twist or turn, providing some relief for torsional stresses. Thespacers 10 and 14 and cooperating plates 40, 58, 60 and 62 may cooperateto limit such torsional movement as well as bending movement. Forexample, a first set of pins may be inserted through the plates 40 and60 and respective engaging spacer surfaces 89 and 88. A second set ofpins may be inserted through the plates 58 and 62 and respectiveengaging spacer surfaces 91 and 90. It may be particularly advantageousto utilize pins made from tantalum, for example to provide x-raymarkers, for example, when the anchor member 4, sleeves and spacers aremade from radiolucent plastics. In other embodiments according to theinvention, the spacers 10 and 14 and cooperating plates 40, 58, 60 and62 may include ribs or fins for insertion into apertures located oncooperating facing surfaces to provide limits on twisting movementbetween such plates and spacers.

With particular reference to FIG. 8, the bumper 18 is substantiallycylindrical, including an outer surface 98 and an inner surface 99forming a substantially cylindrical through bore that opens at planarend surfaces 100 and 101 and operatively extends along the axis A. Thebumper 18 further includes a compression groove 104 that is similar inform and function to the compression grooves 93 and 94 described abovewith respect to the spacers 10 and 14. The bumper 18 is sized and shapedto slidingly receive the core 6 through the inner surface 99. The bumper18 is preferably made from an elastomeric material such as polyurethane.The bumper 18 operatively provides axial tension on the core 6 as willbe described in greater detail below.

With particular reference to FIG. 7, the crimping ring 20 issubstantially cylindrical and includes an outer surface 110 and an innersurface 112 forming a substantially cylindrical through bore that opensat planar end surfaces 114 and 116 and operatively extends along theaxis A. The crimping ring 20 is sized and shaped to receive the elongatecore 6 through the inner surface 112. The crimping ring 20 furtherincludes a pair of crimp or compression grooves 120 that are pressableand deformable inwardly toward the axis A upon final tensioning of thecore 6 and compression of the spacers 10 and 14 and the bumper 18 duringassembly of the assembly 1. The crimping ring 20 is preferably made froma stiff, but deformable material, including metals and metal alloys.

The illustrated dynamic connecting member assembly 1 having apre-tensioned core 6 cooperates with at least three bone anchors, suchas polyaxial bone screws, generally 25 as shown in FIG. 13. In use, thethree bone screws 25 are implanted into vertebrae (not shown). Eachvertebra may be pre-drilled to minimize stressing the bone. Furthermore,when a cannulated bone screw shank is utilized, each vertebra will havea guide wire or pin inserted therein that is shaped for the bone screwcannula of the bone screw shank 30 and provides a guide for theplacement and angle of the shank 30 with respect to the cooperatingvertebra. A further tap hole may be made and the shank 30 is then driveninto the vertebra by rotation of a driving tool (not shown) that engagesa driving feature on or near a top portion of the shank 30. It isforeseen that both the screws 25 and the longitudinal connecting memberassembly 1 may be inserted in a conventional, percutaneous or otherminimally invasive surgical manner.

With particular reference to FIGS. 1, 2 and 6, the longitudinalconnecting member assembly 1 is assembled to provide a pre-tensionedcore 6 and pre-compressed spacers 10 and 14 and bumper 18 prior toimplanting the assembly 1 in a patient. This is accomplished by firstproviding the anchor member 4 that has a core 6 that is longer in theaxial direction A than the core 6 illustrated in the drawing figures.The spacer 10 is first loaded onto the core 6 by inserting the core 6end 38 into the bore defined by the inner surface 82 with the face 89directed toward the buttress plate 40. The spacer 10 is moved along thecore 6 until the surface 86 contacts the surface 48. The sleeve 12 isthen threaded onto the core 6 with the face 72 of the plate 60 facingthe end surface 88 of the spacer 10. The core 6 is received in the boredefined by the inner cylindrical surface 54 and the sleeve 12 is movedalong the core 6 until the plate surface 72 abuts the spacer surface 88.The spacer 14 is thereafter loaded onto the core 6 by inserting the core6 end 38 into the bore defined by the inner surface 84 with the face 91facing the toward the end plate 58 of the sleeve 12. The spacer 14 ismoved along the core 6 until the surface 91 contacts the surface 70. Thesleeve 16 is then threaded onto the core 6 with the face 74 of the plate62 facing the end surface 90 of the spacer 14. The core 6 is received inthe bore defined by the inner cylindrical surface 56 and the sleeve 16is moved along the core 6 until the plate surface 74 abuts the spacersurface 90. The bumper 18 is thereafter loaded onto the core 6 byinserting the core 6 end 38 into the bore defined by the inner surface99 with the face 101 facing the toward the surface 76 of the sleeve 16.The bumper 18 is moved along the core 6 until the surface 101 contactsthe surface 76. The crimping ring 20 is thereafter loaded onto the core6 by inserting the core 6 end 38 into the bore defined by the innersurface 112 with the face 116 facing the toward the surface 100 of thebumper 18. The crimping ring 20 is moved along the core 6 until thesurface 116 contacts the surface 100. It is noted that due to thesymmetrical nature of the sleeve 12, the spacer 14, the bumper 18 andthe crimping ring 20, these components may be loaded onto the core 6from either side thereof.

After the crimping ring 20 is loaded onto the core 6, manipulation tools(not shown) are used to grasp the core 6 near the end 38 and at the boneanchor attachment portion 8, placing tension on the core 6. Furthermore,the spacer 10, the sleeve 12, the spacer 14, the sleeve 16, the bumper18 and the crimping ring 20 are moved toward the buttress plate 40 andinto contact with one another. Axial compressive force may also beplaced on the components loaded on the core 6, followed by deforming thecrimping ring at the crimp grooves 120 and against the core 6. When themanipulation tools are released, the crimping ring 20, now firmly andfixedly attached to the core 6 holds the spacers 10 and 14 and thebumper 18 in compression and the spacers and bumper place axial tensionforces on the core 6, resulting in a dynamic relationship between thecore 6 and the spacers 10, 14 and the bumper 18. The tension on the core6 is advantageously balanced and uniform as the spacers 10 and 16 areslidable with respect to the core 6, but also are limited by thebuttress plate of the anchor member 4 and end plates of the sleeves 12and 16. Furthermore, the bumper 18 that is compressed between the sleevesurface 76 and the crimping ring surface 116 is also slidable withrespect to the core 206. The spacers 10 and 14 and the bumper 18 place adistractive force on the core 6 along the axis A and between thebuttress plate 40 and the crimping ring 20, but also are movable withrespect to the core 6, thus being able to respond to jolting and otherbody movements and thereafter spring back into an originally setlocation. The sleeves 12 and 16 that may compress slightly, but are morerigid than the spacers 10 and 14, keep the spacers 10 and 14 in anapproximate desired axially spaced relation. However, the spacers 10 and14 also advantageously slide along the core 6 in response to outsideforces. The core 6 is then trimmed to be approximately flush with theend surface 114 of the crimping ring 20.

With reference to FIG. 13, the pre-loaded connecting member assembly 1is eventually positioned in an open, percutaneous or other less invasivemanner in cooperation with the at least three bone screws 25 with thespacers 10 and 14 being disposed between and spaced from the bone screws25 and with the portion 8 and sleeves 12 and 16 each being locatedwithin a U-shaped channel of a cooperating bone screw receiver 31. Oncea desired position is attained, a closure structure 27 is then insertedinto and advanced between the arms of each of the bone screw receivers31 until appropriately tightened.

The assembly 1 is thus substantially dynamically loaded and orientedrelative to the cooperating vertebra, providing relief (e.g., shockabsorption) and protected movement with respect to flexion, extension,distraction and compressive forces placed on the assembly 1 and thethree connected bone screws 25. The slender core 6 allows for sometwisting or turning, providing some relief for torsional stresses.Furthermore, the compressed spacers 10 and 14 place some limits ontorsional movement as well as bending movement, to provide spinalsupport. The pre-loaded core 6 (in tension) and spacers 10, 14 andbumper 18 (in compression) allow for compression and some extension ofthe assembly 1 located between the two bone screws 25, e.g., shockabsorption.

If removal of the assembly 1 from any of the bone screw assemblies 25 isnecessary, or if it is desired to release the assembly 1 at a particularlocation, disassembly is accomplished by using the driving tool (notshown) with a driving formation cooperating with the closure structure27 internal drive or cooperating set screw internal drive to rotate andremove the closure structure 27 from the receiver 31. Disassembly isthen accomplished in reverse order to the procedure described previouslyherein for assembly.

Eventually, if the spine requires more rigid support, the connectingmember assembly 1 according to the invention may be removed and replacedwith another longitudinal connecting member, such as a solid rod, havingthe same diameter as the portion 8 and the sleeves 12 and 16, utilizingthe same receivers 31 and the same or similar closure structures 27.Alternatively, if less support is eventually required, a less rigid,more flexible assembly, for example, an assembly 1 having componentsmade of a more flexible material, but with the same diameter sleeves asthe assembly 1, may replace the assembly 1, also utilizing the same bonescrews 25.

With reference to FIGS. 14-17, an alternative embodiment of a dynamiclongitudinal connecting member, generally 201, includes an anchormember, generally 204, having an elongate segment or inner core 206 anda bone anchor attachment portion 208; an elastic spacer 210; a sleeve216; an elastic bumper 218; and a crimping ring 220; all substantiallysymmetrically aligned with respect to a central axis B of the anchormember 204. The elongate core 206 of the anchor member 204 is receivablewithin the spacer 210, the sleeve 216, the bumper 218 and the crimpingring 220. Thus, the axis B of the anchor member 204 is also the axis ofthe fully assembled assembly 201. When fully assembled and fixed withall components fixed in position as shown in FIG. 14, the inner core 206is in tension and the spacer 210 and the bumper 218 are in compression.

In the illustrated embodiment, the anchor member 204 is substantiallysimilar to the anchor member 4 previously described herein with respectto the assembly 1. Therefore, the member 204 includes the core 206, thebone anchor attachment portion 208 and an integral buttress plate 240identical or substantially similar in size and shape to the respectivecore 6, attachment portion 8 and buttress plate 40 of the anchor member4 previously described herein. The member 204 differs from the member 4only in the length of the bone anchor attachment portion 208. Theportion 208 is longer than the similar portion 8 of the member 4 suchthat at least two bone screws 25 are attachable to the portion 208 asillustrated in FIG. 17 while only one bone screw 25 is attached to theportion 8 of the assembly 1. The spacer 210 is identical orsubstantially similar to the spacer 10 illustrated in FIGS. 11 and 12and previously described herein. The sleeve 216 is identical orsubstantially similar to the sleeve 16 illustrated in FIG. 4 andpreviously described herein, having an outer cylindrical surface 252, aninner cylindrical surface 256 defining a through bore and an end plate262 identical or substantially similar to the respective outercylindrical surface 52, inner cylindrical surface 56 and end plate 62 ofthe sleeve 16 previously described herein. The bumper 218 and thecrimping ring 220 are identical or substantially similar to therespective bumper 18 and the crimping ring 20 previously describedherein with respect to the assembly 1.

The assembly 201 is assembled in a manner substantially similar to themanner of assembly previously described herein with respect to theassembly 1, the assembly 201 however, does not include a second spaceror second sleeve. Therefore, the core 206 is first received within athrough bore of the spacer 210, then within the inner cylindricalsurface 256 of the sleeve 216, followed by an inner through bore of thebumper 218 and then an inner through bore of the crimping ring 220.Similar to what has been described previously with respect to theassembly 1, the core 206 is initially of a longer length measured alongthe axis B than is shown in the drawing figures, allowing for amanipulation tool to grasp the core 206 near an end thereof that extendsthrough the crimping ring bore. The core 206 is tensioned and/or thespacer 210 and bumper 220 are compressed, followed by deformation of thecrimping ring 220 against the core 206. The core 206 is then trimmedsubstantially flush to the crimping ring 220. The assembly is now indynamic relationship with the core 206 being in tension while the spacer210 that is slidable with respect to the core 206 is compressed betweenthe plates 240 and 262 and the bumper 218 that is also slidable withrespect to the core 206 is compressed between the sleeve 216 and thecrimping ring 220; the spacer 210 and the bumper 218 placing adistractive force on the core 206 along the axis B and between thebuttress plate 240 and the crimping ring 220. The assembly 201 may thenbe implanted, cooperating with three bone screws 25 as illustrated inFIG. 17 and as previously described herein with respect to the assembly1. Unlike the assembly 1 illustrated in FIG. 13 that provides for a moredynamic and flexible connection between all three illustrated bonescrews 25, the assembly 201 provides for dynamic stabilization betweenfirst and second bone screws 25 and a more rigid connection between thesecond bone screw 25 and a third bone screw 25 as both the second andthird bone screws are attached to the rigid attachment portion 208.

With reference to FIG. 18, a third embodiment of a dynamic longitudinalconnecting member assembly, generally 301 is illustrated. The assembly301 includes an anchor member 304 having an inner core 306 and a boneanchor attachment portion 308; a spacer 310, a sleeve 316, a bumper 318and a crimping ring 320. The illustrated spacer 310, sleeve 316, bumper318 and crimping ring 320 are identical to the spacer 210, sleeve 216,bumper 218 and crimping ring 220 previously described herein withrespect to the assembly 201. The anchor member 304 is identical to theanchor member 204 with the exception that the bone anchor attachmentportion 308 is of a length to receive three bone screw receivers 31therealong while the portion 208 is sized to receive two bone screwreceivers 31. It is foreseen that longitudinal connecting memberassemblies according to the invention may be of a variety of lengths forcooperation with a plurality of bone screws 25, either along a rigid endportion, such as the portion 308 shown in FIG. 18, or along dynamicportions that include one or more spacers and one or more sleeves, suchas the sleeves 12 and 16 for attachment to bone screws 25 or other boneanchors. It is foreseen that such sleeves may also be a variety oflengths for attachment to one or more bone anchors along a length of theindividual sleeve.

With reference to FIGS. 19 and 20, fourth and fifth embodiments of adynamic longitudinal connecting member assembly of the invention areillustrated. With reference to FIG. 19, an assembly 1′ is illustratedthat is substantially similar to the assembly 1 previously describedherein with an anchor member, generally 4′, having an inner coreextension 6′ fixed to a bone anchor attachment portion 8′; spacers 10′and 14′; sleeves 12′ and 16′; a bumper 18′ and a crimping ring 20′, allaligned along an axis A′. The illustrated spacers 10′ and 14′, sleeves12′ and 16′, bumper 18′ and crimping ring 20′ are identical orsubstantially similar to the respective spacers 10 and 14, sleeves 12and 16, bumper 18 and crimping ring 20 of the assembly 1. The embodiment1′ differs from the assembly 1 only in how the core extension 6′ isfixed to the bone anchor attachment portion 8′. In the assembly 1′ theattachment portion 8′ includes a threaded aperture T and the coreextension 6′ includes an outer threaded portion 36′ that mates with thethreaded aperture T, fixing the core extension 6′ to the portion 8′ uponrotation of the core extension 6′ about the axis A′ within the apertureT.

With reference to FIG. 20, another embodiment of the invention, anassembly 201′, is shown that is substantially similar to the assembly201 illustrated in FIGS. 14-17. The assembly 201′ includes an anchormember, generally 204′, having an inner core extension 206′ fixed to abone anchor attachment portion 208′; a spacer 210′; a sleeve 216′; abumper 218′ and a crimping ring 220′, all aligned along an axis B′. Theillustrated spacer 210′, sleeve 216′, bumper 218′ and crimping ring 220′are identical or substantially similar to the respective spacer 210,sleeve 216, bumper 218 and crimping ring 220 of the assembly 201. Theembodiment 201′ differs from the assembly 201 only in how the coreextension 206′ is fixed to the bone anchor attachment portion 208′. Inthe assembly 201′ the attachment portion 208′ includes a threadedaperture T′ and the core extension 206′ includes an outer threadedportion 236′ that mates with the threaded aperture T′, fixing the coreextension 206′ to the portion 208′ upon rotation of the core extension206′ about the axis B′ within the aperture T′. It is noted that theaperture T shown in FIG. 19 extends completely through the portion 8′while the aperture T′ shown in FIG. 20 extends substantially into theportion 208′ along the axis B′, but does not extend therethrough.

With reference to FIGS. 21-23, another embodiment of a connecting memberaccording to the invention, an assembly 401 is shown that includes thesame or similar components to the assemblies 1 and 201, for example,previously described herein. However, the components are sized such thatthe resulting assembly 401 has a constant outer diameter along an entirelength thereof. Thus, the assembly 401 generally designates a non-fusiondynamic stabilization longitudinal connecting member assembly accordingto the present invention having an anchor member, generally 404, thatincludes an elongate segment or inner core 406 integral with orotherwise fixed to a bone anchor attachment portion 408; an end spaceror stop 410; a second elastic spacer 411; a rigid sleeve 412; and acrimping ring 420; all substantially symmetrically aligned with respectto a central axis of the anchor member 404. The elongate core 406 of theanchor member 404 is receivable within the spacers 410 and 411, thesleeve 412 and the crimping ring 420. Thus, the central axis of theanchor member 404 is also the axis of the fully assembled assembly 401.Although not shown, the core 406 may be made of a slightly longer lengthand an elastic bumper, similar to the bumper 18 of the assembly 1 (butof a different inner diameter, such as the bumper 418′ shown in FIG. 24)may be placed between the sleeve 412 and the crimping ring 420. The core406, anchor attachment portion 408, spacers 410 and 411, sleeve 412 andcrimping ring 420 are substantially similar in form and function to therespective core 6, anchor attachment portion 8, spacer 10, sleeve 12 andcrimping ring 20 of the assembly 1. In the illustrated embodiment 401,the two spacers 410 and 411 may be made out of the same or differentmaterials. For example, it may be desirable to make the spacer 410 of amore rigid material than the spacer 411 to provide more of a stop orbarrier between the anchor attachment portion 408 and the spacer 411 inlight of the reduced size of the components of the assembly 401 ascompared to the assembly 1 and the fact that the assembly 401 does notinclude a buttress plate such as the buttress plate 40 of the assembly1. It is foreseen that in certain embodiments of the invention, the twospacers 410 and 411 may be replaced by a single spacer. Furthermore,rather than a gradual decrease in diameter from the portion 408 to thecore 406 shown in the drawings, the anchor attachment portion 408 andthe core 406 may be configured in a more abrupt or stepped manner,forming a small stop or abutment surface disposed perpendicular to thecentral axis of the anchor member 404.

Similar to the assembly 1, the assembly 404, when fully assembled, hasthe inner core 406 in tension and at least the spacer 411 incompression, with the ring 420 crimped against the core 406. The dynamicconnecting member assembly 401 cooperates with at least two bone anchors(not shown), such as the anchors 25, the anchors being attached to theportion 408 and the rigid sleeve 412.

With reference to FIG. 24, another embodiment of a connecting memberaccording to the invention, an assembly 401′, is shown that issubstantially similar to the assembly 401. The assembly 401′ differsfrom the assembly 401 only that the assembly 401′ includes a bumper418′, a pair of spacers 411′ identical or substantially similar to thespacer 411 and a pair of rigid sleeves 412′ identical or substantiallysimilar to the sleeve 412, allowing for a bone screw 25 to be attachedto each sleeve 412′ as well as to the anchor portion 408′, for a totalof at least three bone screws 25. One spacer 411′ is disposed betweeneach bone screw 25. Thus, the assembly 401′ includes an anchor member404′ that includes an elongate segment or inner core (not shown, butsubstantially similar to the core 406 shown in FIG. 22) and an integralbone anchor attachment portion 408′; an end spacer or stop 410′; a pairof elastic spacers 411′; a pair of rigid sleeves 412′; and a crimpingring 420′; all substantially symmetrically aligned with respect to acentral axis of the anchor member 404′. The elongate core of the anchormember 404′ is receivable within the end spacer 410′, the spacers 411′,the sleeves 412′ and the crimping ring 420′ as well as the elasticbumper 418′ that is similar in form and function to the bumper 18 of theassembly 1. Thus, the anchor member 404′, spacers 411, sleeve 412,bumper 418′ and crimping ring 420 are substantially similar in form andfunction to the respective anchor member 4, spacer 10, sleeve 12, bumper18 and crimping ring 20 of the assembly 1. Similar to the assembly 401,the assembly 401′ end spacer or stop 410′ may be elastic like thespacers 411′ or may be made of a more rigid material in order tofunction in a manner similar to the buttress plate 40 of the assembly 1.

With reference to FIGS. 25-38, the reference numeral 501 generallydesignates another embodiment of a non-fusion dynamic stabilizationlongitudinal connecting member assembly according to the presentinvention. The connecting member assembly 501 includes an anchor member,generally 504, having an elongate segment or inner core or coreextension 506 and a bone anchor attachment portion 508; an elasticspacer 510; a sleeve 512; an elastic bumper 518; and a crimping member520; all substantially symmetrically aligned with respect to a centralaxis AA of the anchor member 504. The elongate core 506 of the anchormember 504 is receivable within the spacer 510, the sleeve 512, thebumper 518 and the crimping member 520. Thus, the axis AA of the anchormember 504 is also a central axis of the fully assembled assembly 501.As will be described in greater detail below, when fully assembled andfixed with all components fixed in position as shown in FIG. 25, theinner core 506 is in tension and the spacer 510 and the bumper 518 arein compression.

As illustrated in FIG. 38, the dynamic connecting member assembly 501cooperates with at least two bone anchors, such as the polyaxial bonescrews, generally 525 and cooperating closure structures 527, theassembly 501 being captured and fixed in place at the anchor portion 508and the sleeve 512 by cooperation between the bone screws 525 and theclosure structures 527. All of the embodiments according to theinvention illustrated in FIGS. 25-52 are shown with the same bone screws525 and cooperating closure structures 527, however, as more fullydiscussed below, a wide variety of bone anchors may be used withconnecting members according to the invention. For example, because theanchor portion 508 and the sleeve 512 of the assembly 501 havesubstantially solid and planar surfaces, the connecting member assembly501 may be used with a wide variety of bone screws and other boneanchors that closely receive the planar surfaces of the assembly 501,including fixed, monoaxial bone screws, hinged bone screws, polyaxialbone screws, and bone hooks and the like, with or without compressioninserts, that may in turn cooperate with a variety of closure structureshaving threads, flanges, or other structure for fixing the closurestructure to the bone anchor, and may include other features, forexample, external or internal drives, break-off tops and inner setscrews. The bone anchors, closure structures and the connecting memberassembly 501 are then operably incorporated in an overall spinal implantsystem for correcting degenerative conditions, deformities, injuries, ordefects to the spinal column of a patient.

The illustrated polyaxial bone screws 525 each include a shank 530 forinsertion into a vertebra (not shown), the shank 530 being pivotallyattached to an open receiver or head 531. The shank 530 includes athreaded outer surface and may further include a central cannula orthrough-bore disposed along an axis of rotation of the shank. Thethrough bore provides a passage through the shank interior for a lengthof wire or pin inserted into the vertebra prior to the insertion of theshank 530, the wire or pin providing a guide for insertion of the shank530 into the vertebra. The receiver 531 includes a pair of spaced andgenerally parallel arms that form an open squared off U-shaped channeltherebetween that is open at distal ends of such arms. The receiver armseach include radially inward or interior surfaces that have adiscontinuous guide and advancement structure mateable with cooperatingstructure on the closure structure 527. The guide and advancementstructure may be a partial helically wound flangeform configured to mateunder rotation with a similar structure on the closure structure 527 ora buttress thread, a square thread, a reverse angle thread or otherthread like or non-thread like helically wound advancement structuresfor operably guiding under rotation and advancing the closure structure527 downward between the receiver arms and having such a nature as toresist splaying of the receiver arms when the closure 527 is advancedbetween the receiver arms.

The shank 530 and the receiver 531 may be attached in a variety of ways.For example, a threaded capture connection as described in U.S. PatentPub. No. 2007/0055244, and incorporated by reference herein, may be usedwherein the bone screw shank includes an outer helical thread mateablewith an inner helical thread of a retaining structure disposed withinthe receiver. The shank 530 of the illustrated bone screw 525 is toploaded into the receiver 531 and includes an upper portion 536 that hasa partially spherical surface that is slidingly mateable with acooperating inner surface of the receiver 531, allowing for a wide rangeof pivotal movement between the shank 530 and the receiver 531. Top orbottom loaded polyaxial bone screws for use with the assembly 501 mayinclude other types of capture connections, including but not limitedto, other threadably connected, spline connected, or cam connected shankupper portions mateable with a retainer structure or ring that is inturn slidingly mateable with the inner surface of the receiver 531,frictional connections utilizing frusto-conical or polyhedral capturestructures, and other types of integral top or downloadable shanks.Also, as indicated above, polyaxial and other bone screws for use withconnecting members of the invention may have bone screw shanks thatdirectly engage the elongate connecting member or, as illustrated,include at least one compression member, such as the lower insert 538that includes a partially spherical base that engages the substantiallyspherical upper portion of the bone screw shank 536 and also engages thebone anchor attachment portion 508 or the sleeve 512 to securely holdthe connecting member assembly 501 within the receiver 531 and/orcooperate with the closure structure 527 to fix the bone screw shank 530at a desired angle with respect to the bone screw receiver 531. Asillustrated in FIG. 38 and also shown in FIG. 48, the insert 538includes spaced parallel walls disposed perpendicular to a bottomseating surface for closely holding the flat surfaced anchor attachmentportion 508 or the flat surfaced sleeve 512 at a location slightlyspaced from the squared off opening of the receiver 531.

Although the closure structure 527 for use with the assembly 501 of thepresent invention is illustrated with the polyaxial bone screw 525having an open receiver or head 531, it foreseen that a variety ofclosure structures may be used in conjunction with any type of medicalimplant having an open or closed head or receiver, including monoaxialbone screws, hinged bone screws, hooks and the like used in spinalsurgery.

To provide a biologically active interface with the bone, the threadedshank 530 may be coated, perforated, made porous or otherwise treated.The treatment may include, but is not limited to a plasma spray coatingor other type of coating of a metal or, for example, a calciumphosphate; or a roughening, perforation or indentation in the shanksurface, such as by sputtering, sand blasting or acid etching, thatallows for bony ingrowth or ongrowth. Certain metal coatings act as ascaffold for bone ingrowth. Bio-ceramic calcium phosphate coatingsinclude, but are not limited to: alpha-tri-calcium phosphate andbeta-tri-calcium phosphate (Ca₃(PO₄)₂, tetra-calcium phosphate(Ca₄P₂O₉), amorphous calcium phosphate and hydroxyapatite(Ca₁₀(PO₄)₆(OH)₂). Coating with hydroxyapatite, for example, isdesirable as hydroxyapatite is chemically similar to bone with respectto mineral content and has been identified as being bioactive and thusnot only supportive of bone ingrowth, but actively taking part in bonebonding.

With further reference to FIG. 38, the closure structure 527 can be anyof a variety of different types of closure structures for use inconjunction with the present invention with suitable mating structure onthe interior surface of the upstanding arms of the receiver 531. Theillustrated closure structure 527 is rotatable between the spaced arms,but it is foreseen that it could be a slide-in closure structure. Theillustrated closure structure 527 is substantially cylindrical andincludes an outer helically wound guide and advancement structure in theform of a flange form that may take a variety of forms, including thosedescribed in Applicant's U.S. Pat. No. 6,726,689, the disclosure ofwhich is incorporated herein by reference. It is also foreseen thataccording to the invention the closure structure guide and advancementstructure could alternatively be a buttress thread, a square thread, areverse angle thread or other thread like or non-thread like helicallywound advancement structure for operably guiding under rotation andadvancing the closure structure 527 downward between the receiver armsand having such a nature as to resist splaying of the arms when theclosure structure 527 is advanced into the squared off U-shaped channelformed by the arms. The closure 527 may further include an inner setscrew with an internal drive in the form of an aperture utilized forassembly of the set screw and removal of the entire closure 527. It isforeseen that the closure structure may alternatively include anon-helically wound locking or cam structure that may also include aflanged lip. It is also foreseen that the closure structure 527 mayalternatively include an external drive, such as a break-off headdesigned to allow such a head to break from a base of the closure at apreselected torque, for example, 70 to 140 inch pounds. Such a closurestructure would also include a base having an internal drive to be usedfor closure removal. In the illustrated embodiments, the closure 527 hasa planar bottom surface that engages the insert 538 as well as the boneanchor portion 508 or the sleeve 512 for consistent secure locking ofthe polyaxial screw mechanism, the insert 538 pressing against the shankupper portion 536 that in turn presses against an inner surface of thereceiver 531. It is also foreseen that the closure structure may have aroughened or point and rim structure to aid in frictionally engaging thelongitudinal connecting member.

Returning to the longitudinal connecting member assembly 501 illustratedin FIGS. 25-38, the assembly 501 is elongate, with the inner core 506being a substantially solid, smooth and uniform bar of substantiallysquare or rectangular cross-section. The core 506 may have a variety ofcross-sectional geometries including polygonal and curvate. It ispreferred that the cross-section be non-circular. However, a curvatecross-section, such as an oval or elliptical shape is acceptable. Aswill be described in greater detail below, the non-circular shape of thecore 506 advantageously provides for torsion control of the assemblywhereas a similar assembly made with a core of a circular cross sectionmay tend to slip or rotate with respect to the other components of theassembly 501 when the assembly 501 is placed under torsional forces.Such a connecting member may require further structure in the form ofpegs, pins or adhesives to more firmly connect an anchor member (similarto the anchor 504 but with circular cross-section) with an outer spacer(similar to the spacer 510 but with circular cross-section), forexample.

The anchor attachment portion 508 may be made from metal, metal alloysor other suitable materials, including plastic polymers such aspolyetheretherketone (PEEK), ultra-high-molecular weight-polyethylene(UHMWP), polyurethanes and composites, including composites containingcarbon fiber. It is noted that although an anchor member 504 isillustrated in which the components 506 and 508 are integral, the coreextension 506 and the anchor attachment portion 508 may be made fromdifferent materials, for example, the core extension 506 may be made outof PEEK and fixed or adhered to a bone anchor attachment portion 508made out of titanium. The core 506 and attachment portion 508 eachinclude a small central lumen or through-bore 540 extending along thecentral axis AA. The lumen 540 may be used as a passage through theentire assembly 501 interior for a length of a guide wire for aidinginsertion of the assembly 501 between implanted bone screws 525 in apercutaneous or less invasive procedure.

With particular reference to FIGS. 27-29, the anchor member 504 issubstantially bar-shaped along an entire length thereof along the axisAA and includes at least two or more rectangular cross-sections alongthe length thereof. The illustrated member 504 includes the slender andthus more flexible core 506 of a first rectangular cross-section that isillustrated in the drawings as having a square cross-section with fourouter planar surfaces 543. The core 506 terminates at an end 544. Priorto final assembly, the core 506 is typically of a length greater thanthat shown in the drawing figures so that the core 6 may be grasped by atool (not shown) near the end 544 and pulled along the axis AA in adirection away from the anchor attachment portion 508 in order to placetension on the core 506. Alternatively, the core 506 may be grasped by atool near the end 544 during compression of the spacer 510 and/or bumper518 and crimping of the member 520. As will be described in greaterdetail below, after removal of the tools, the spacer 510 and bumper 518expand along the axis AA, placing the core extension 506 in tension.

The bone anchor attachment portion 508 that is integral with the coreextension 506 has a second rectangular cross-section that is larger thanthe core 506 cross-section and thus the portion 508 is more rigid thanthe core 506. Also with reference to FIGS. 25-29, between the core 506and the portion 508 is a buttress plate 546 that has a rectangularcross-section that is larger than the cross-section of the attachmentportion 508. The buttress plate 546 is integral with and disposedbetween the core 506 and the portion 508. Although the illustratedanchor member 504 is substantially rectangular, it is foreseen that thecore 506, the portion 508 and the plate 546 may have other forms,including but not limited to oval and square cross-sections as well asother curved or polygonal shapes. The bone anchor attachment portion 508is of a length along the axis AA for cooperating with at least one andup to a plurality of bone attachment members, such as the bone screws525, hooks or other types of bone anchors. The portion 508 issubstantially solid and rigid, with opposed planar surfaces 548 andperpendicular cooperating opposed planar surfaces 550. The surfaces 548and 550 terminate at an end 551. In the illustrated embodiment, adistance between the surfaces 548 is slightly greater than a distancebetween the surfaces 550. This is advantageous in situations wherein arelatively stiff bar 508 is desired but space considerations such asvertebrae and tooling placement require a more slender elongateconnector.

The buttress plate 546 includes a first substantially flat and annularface 552 facing away from the core 506 and an opposed parallelsubstantially flat face 554 facing toward the core 506. The faces 552and 554 are disposed substantially perpendicular to the axis AA. Anouter surface 556 of rectangular cross-section extends between the faces552 and 554. A gently sloping transition surface or flange 558 bridgesbetween and connects the surfaces 543 of the core 506 with thesubstantially flat face 554 of the buttress plate 546.

With particular reference to FIGS. 26, 32 and 33, the sleeve 512 issized and shaped to be slidingly received over the core 506 along theaxis AA and has a length measured along the axis AA that is sufficientfor the attachment of at least one bone screw 525 thereon. Similar tothe anchor member 504, the sleeve 512 may be made from metal, metalalloys or other suitable materials, including plastic polymers such aspolyetheretherketone (PEEK), ultra-high-molecular weight-polyethylene(UHMWP), polyurethanes and composites, including composites containingcarbon fiber. The sleeve 512 may be made of the same material as thecooperating core 506, for example, the anchor member 504 and the sleeve512 may be made from PEEK; or, for example, the core 506 may be madefrom one material, such as PEEK, while the sleeve 512 may be made fromanother material, such as a metal (e.g. stainless steel or titanium). Inorder to have low or no wear debris, the sleeve 512 inner surfacesand/or cooperating core 506 outer surfaces may be coated with an ultrathin, ultra hard, ultra slick and ultra smooth coating, such as may beobtained from ion bonding techniques and/or other gas or chemicaltreatments.

The illustrated sleeve 512 has a rectangular cross-section takenperpendicular to the axis AA, having outer opposed planar anchorattachment surfaces 560 and cooperating perpendicular opposed planarattachment surfaces 562. The illustrated sleeve 512 rectangularcross-section is identical or substantially similar to the rectangularcross-section formed by the surfaces 548 and 550 of the bone anchorattachment portion 508. The sleeve 512 further includes inner opposedplanar surfaces 564 and cooperating perpendicular opposed planarsurfaces 566 that define a through-bore for the passage of the core 506therethrough. In the illustrated embodiment, the surfaces 564 and 566are of substantially the same width (measured perpendicular to the axisAA) for being closely slidingly mateable with the surfaces 543 of thecore 506. The sleeve 512 further includes a plate 570 at an end thereof.The illustrated end plate 570 has a rectangular cross-sectionperpendicular to the axis AA partially defined by outer planar surfaces574. The surfaces 574 are sized and shaped to be identical orsubstantially similar to the surfaces 556 of the plate 546 of the anchormember 504. The plate 570 has a planar surface 575 perpendicular to theaxis AA and an opposed terminal planar surface 576. The surfaces 560 and562 terminate at an outer planar surface 578.

With reference to FIGS. 25-27, the elastic spacer 510 and the elasticbumper 518 are sized and shaped to be slidingly received over the core506 and may be made from a variety of elastic materials, including, butnot limited to natural or synthetic elastomers such as polyisoprene(natural rubber), and synthetic polymers, copolymers, and thermoplasticelastomers, for example, polyurethane elastomers such aspolycarbonate-urethane elastomers. In order to have low or no weardebris, the spacer 510 and the bumper 518 inner and side surfaces mayalso be coated with an ultra thin, ultra hard, ultra slick and ultrasmooth coating, such as may be obtained from ion bonding techniquesand/or other gas or chemical treatments.

The illustrated spacer 510 advantageously closely slidingly mates andcooperates with the core 506 of the anchor member 504, providinglimitation and protection of axial movement and torsional control of thecore 506 located between bone screws 525. With particular reference toFIGS. 26, 30 and 31, the illustrated spacer 510 has a pair of opposedplanar outer surface 580 and perpendicular opposed planar cooperatingsurfaces 582. The surfaces 580 and 582 have an outer cross-sectionsimilar or identical in size to the plates 546 and 570. The spacer 510also includes inner surfaces 584 of substantially the same width forminga lumen or through bore of substantially rectangular cross-section withrespect the axis AA. In the illustrated embodiment, the cross-section issubstantially square and slightly larger than the substantially squarecross-section of the core 506. The internal surfaces 584 are furtherdefined by a flared outwardly extending surface 586 sized and shaped forcooperating with the surface 558 of the anchor member 504. The spacer510 includes opposed substantially planar end surfaces 588 and 589. Theflared surface 586 terminates at the end surface 588. When cooperatingwith the core 506, the end surfaces 588 and 589 are substantiallyperpendicular to the axis AA. It is foreseen that in some embodiments,the spacer 510 may be of circular, square, or other outercross-sectional shapes including curved or polygonal shapes. In theillustrated embodiment, the spacer 510 further includes a compressiongroove 590. Spacers according to the invention may include one, none orany desired number of grooves 590 that allow for some additionalcompression of the spacer 510 when pressed upon in an axial direction bythe plates 546 and 570. The illustrated groove 590 is substantiallyuniform and formed in the external surfaces 580 and 582 and extendinginwardly toward the internal surfaces 584. The size of the internalsurfaces 584 allow for some axially directed sliding movement of thespacer 510 with respect to the core surfaces 543 but limits any rotationof the spacer 510 about the axis AA and thus limits twisting movementsbetween the anchor 504, the sleeve 512 and the spacer 510.

With particular reference to FIGS. 25-27 and 34-35, the illustratedbumper 518 is substantially square in cross-section in an operationaldirection perpendicular to the axis AA. The bumper 518 includes outerplanar surfaces 592 and an inner bore also of substantially squarecross-section with respect to the axis AA, the bore formed by innerplanar surfaces 594 sized and shaped to be slightly larger than thesurfaces 543 defining the core 506. The surfaces 592 and 594 terminateat planar end surfaces 596 and 598 that are operatively perpendicular tothe axis AA. The bumper 518 further includes a compression groove 600that is similar in form and function to the compression groove 590described previously herein with respect to the spacer 510. The bumper518 is sized and shaped to slidingly receive the core 506 through theinner surface 594. The bumper 518 is preferably made from an elastomericmaterial such as polyurethane. The bumper 518 operatively provides axialtension on the core 506 as will be described in greater detail below.

With particular reference to FIGS. 25-27 and 36-37, the crimping member520 is substantially square in cross-section taken in a directionperpendicular to the axis AA and includes four substantially planarouter surfaces 602. Four planar inner surfaces 604 form a through borealso of substantially square cross-section, sized and shaped to closelyslidingly receive the planar surfaces 543 of the core 506 along the axisAA. The surfaces 602 and 604 terminate at opposed planar end surfaces606 and 608. The crimping member 520 further includes a pair of opposedcrimp or compression grooves 610 that are pressable and deformableinwardly toward the axis AA upon final tensioning of the core 506 and/orcompression of the spacer 510 and the bumper 518 during assembly of theassembly 501. The crimping member 520 is preferably made from a stiff,but deformable material, including, but not limited to, metals and metalalloys.

The illustrated dynamic connecting member assembly 501 having apre-tensioned core extension 506 cooperates with at least two boneanchors, such as the polyaxial bone screws, generally 525 as shown inFIG. 38. In use, the bone screws 525 are implanted into vertebrae (notshown). Each vertebra may be pre-drilled to minimize stressing the bone.Furthermore, when a cannulated bone screw shank is utilized, eachvertebra will have a guide wire or pin inserted therein that is shapedfor the bone screw cannula of the bone screw shank 530 and provides aguide for the placement and angle of the shank 530 with respect to thecooperating vertebra. A further tap hole may be made and the shank 530is then driven into the vertebra by rotation of a driving tool (notshown) that engages a driving feature on or near a top portion of theshank 530. It is foreseen that both the screws 525 and the longitudinalconnecting member assembly 501 may be inserted in a conventional,percutaneous or other minimally invasive surgical manner.

With particular reference to FIGS. 25-27, the longitudinal connectingmember assembly 501 is assembled to provide a pre-tensioned core 506 andpre-compressed spacer 510 and bumper 518 prior to implanting theassembly 501 in a patient. This is accomplished by first providing theanchor member 504 that has a core 506 that is longer in the axialdirection AA than the core 506 illustrated in the drawing figures. Thespacer 510 is first loaded onto the core 506 by inserting the core 506end 544 into the bore defined by the inner surfaces 584 with the spacerend face 588 directed toward the buttress plate 546. The spacer 510 ismoved along the core 506 until the surface 586 contacts the surface 558.The sleeve 512 is then threaded onto the core 506 with the face 576 ofthe plate 570 facing the end surface 589 of the spacer 510. The core 506is received in the bore defined by the inner planar surfaces 564 and 566and the sleeve 512 is moved along the core 506 until the plate surface576 abuts the spacer surface 589. The bumper 518 is thereafter loadedonto the core 506 by inserting the core 506 end 544 into the boredefined by the inner surfaces 594 with the face 596 facing the towardthe surface 578 of the sleeve 512. The bumper 518 is moved along thecore 506 until the surface 596 contacts the surface 578. The crimpingmember 520 is thereafter loaded onto the core 506 by inserting the core506 end 544 into the bore defined by the inner surfaces 604 with theface 606 facing the toward the surface 598 of the bumper 518. Thecrimping member 520 is moved along the core 506 until the surface 606contacts the surface 598. It is noted that due to the symmetrical natureof the sleeve 512, the spacer 514, the bumper 518 and the crimpingmember 520, these components may be loaded onto the core 506 from eitherside thereof. However, if, as in the illustrated embodiment, the boneanchor attachment portion 508, the spacer 510 and the sleeve 512 are notof square cross-section, such components 508, 510 and 512 are assembledon the core 506 in alignment with the surfaces 548, 580 and 560 beingloaded on the core to be in parallel planes. As illustrated in FIGS. 25and 26, in the illustrated embodiment, such alignment places thesurfaces 548 and 560 in substantially the same plane. Likewise, suchassembly places the surfaces 550, 582 and 562 in parallel with thesurfaces 550 and 562 being in substantially the same plane.

After the crimping member 520 is loaded onto the core 506, manipulationtools (not shown) are used to grasp the core 506 near the end 544 and atthe bone anchor attachment portion 508, placing tension on the core 506.Furthermore, the spacer 510, the sleeve 512, the bumper 518 and thecrimping member 520 are moved toward the buttress plate 540 and intocontact with one another. Alternatively, or in addition, axialcompressive force is placed on the components loaded on the core 506,followed by deforming the crimping member at the crimp grooves 610 andagainst the core 506. When the manipulation tools are released, thecrimping member 520, now firmly and fixedly attached to the core 506holds the spacer 510 and the bumper 518 in compression and the spacersand bumper place axial tension forces on the core 506, resulting in adynamic relationship between the core 506 and the spacer 510 and bumper518. The tension on the core 506 is advantageously balanced and uniformas the spacer 510 is slidable with respect to the core 506, but also arelimited by the buttress plate of the anchor member 504 and end plate ofthe sleeve 512. Furthermore, the bumper 518 that is compressed betweenthe sleeve surface 578 and the crimping member surface 606 is alsoslidable with respect to the core 506. The spacer 510 and the bumper 518place a distractive force on the core 506 along the axis AA and betweenthe buttress plate 546 and the crimping member 520, but also are movablewith respect to the core 506, thus being able to respond to jolting andother body movements and thereafter spring back into an originally setlocation.

The sleeve 512 may compress slightly, but is more rigid than the spacer510 and bumper 518 and thus keeps the spacers 510 and bumper 518 in anapproximate desired axially spaced relation. However, the spacer 510also advantageously slides along the core 506 in response to outsideforces. The core 506 is then trimmed to be approximately flush with theend surface 608 of the crimping member 520.

With reference to FIG. 38, the pre-loaded connecting member assembly 501is eventually positioned in an open, percutaneous or other less invasivemanner in cooperation with the at least two bone screws 525 with thespacer 510 being disposed between and spaced from the bone screws 525and with the portion 508 and sleeve 512 each being located within asquared-off U-shaped channel of a cooperating bone screw receiver 531.Once a desired position is attained, a closure structure 527 is theninserted into and advanced between the arms of each of the bone screwreceivers 531 until appropriately tightened.

The assembly 501 is thus substantially dynamically loaded and orientedrelative to the cooperating vertebra, providing relief (e.g., shockabsorption) and protected movement with respect to flexion, extension,distraction and compressive forces placed on the assembly 501 and theconnected bone screws 525. The slender core extension 506 allows forsome twisting providing some relief for torsional stresses. However, thefact that the core 506 is of a non-round cross-section and cooperateswith through bores of the other assembly components that are alsonon-round and closely slidingly mate with the core 506 alsoadvantageously provides limits to rotational or twisting movement of theassembly 501 in response to torsional forces. Furthermore, thecompressed spacer 510 places some limits on torsional movement as wellas bending movement, to provide spinal support. The pre-loaded core 506(in tension) and spacer 510 and bumper 518 (in compression) allow forcompression and some extension of the assembly 501 located between thetwo bone screws 525, e.g., shock absorption.

If removal of the assembly 501 from any of the bone screw assemblies 525is necessary, or if it is desired to release the assembly 501 at aparticular location, disassembly is accomplished by using the drivingtool (not shown) with a driving formation cooperating with the closurestructure 527 internal drive or cooperating set screw internal drive torotate and remove the closure structure 527 from the receiver 531.Disassembly is then accomplished in reverse order to the proceduredescribed previously herein for assembly.

Eventually, if the spine requires more rigid support, the connectingmember assembly 501 according to the invention may be removed andreplaced with another longitudinal connecting member, such as a solidcylindrical or bar-like rod, having the same diameter or width as thewidth of the bar-like portion 508 and the sleeve 512, utilizing the samereceivers 531 and the same or similar closure structures 527.Alternatively, if less support is eventually required, a less rigid,more flexible assembly, for example, an assembly 501 having componentsmade of a more flexible material, but with the same size sleeves as theassembly 501, may replace the assembly 501, also utilizing the same bonescrews 525.

With reference to FIGS. 39-44, another embodiment of a dynamiclongitudinal connecting member of the invention, generally 701, includesan anchor member, generally 704, having an elongate segment or innercore 706 and a bone anchor attachment portion 708; an elastic spacer710; a sleeve 716; an elastic bumper 718; and a crimping member 770; allsubstantially symmetrically aligned with respect to a central curvateaxis BB of the anchor member 704 as unlike the core 506 of the assembly501, the core 706 of the assembly 701 is bent primarily at a locationnear the portion 708. The elongate core 706 of the anchor member 704 isreceivable within the spacer 710, the sleeve 716, the bumper 718 and thecrimping member 720. Thus, the central curvate axis BB of the anchormember 704 is also the axis of the fully assembled assembly 701. Whenfully assembled and fixed with all components fixed in position as shownin FIG. 39, the inner core 706 is in tension and the spacer 710 and thebumper 718 are in compression.

In the illustrated embodiment, the anchor member 704 is substantiallysimilar to the anchor member 504 previously described herein withrespect to the assembly 501. Therefore, the member 704 includes the core706, the bone anchor attachment portion 708 and an integral buttressplate 746 identical or substantially similar in size and shape to therespective core 506, attachment portion 508 and buttress plate 546 ofthe anchor member 504 previously described herein. The member 704differs from the member 504 only in the fact that the core 706 is bentadjacent the buttress plate 746.

The sleeve 712 is identical or substantially similar to the sleeve 512illustrated in FIGS. 32 and 33 and previously described herein, havingan outer planar surfaces 760 and 762, inner planar surfaces 764 and 766defining a through bore and an end plate 770 identical or substantiallysimilar to the respective outer surfaces 560 and 562, inner surfaces 564and 566 and end plate 570 of the sleeve 512 previously described herein.The bumper 718 and the crimping member 720 are identical orsubstantially similar to the respective bumper 518 and the crimpingmember 520 previously described herein with respect to the assembly 501.

The spacer 710 is operatively located between the buttress plate 746 andthe sleeve plate 770 in a manner similar to the spacer 510 locatedbetween the plates 546 and 570 of the assembly 501. The spacer 710 isalso made from materials similar to the materials from which the spacer10 is made. The spacer 710 further includes inner planar surfaces 784and a flanged surface 786 forming a through bore for receiving the core706, such surfaces 784 and 786 being substantially similar in form andfunction to the surfaces 584 and 586 previously described herein withrespect to the spacer 510 with the exception that the through bore maybe further modified to follow the curvature of the bent core 706. Also,the spacer 710 is of a different shape than the spacer 510. The spacer710 includes a pair of opposed planar surfaces 790 that are trapezoidalin shape. The surfaces 790 run parallel to the through bore formed bythe planar surfaces 784, such bore terminating at opposed load-bearingend surfaces 792 and 794. The surfaces 792 and 794 are not parallel,each directed toward one another and terminating at a small top(operatively posterior with respect to the spine) surface 796 andsloping in a direction away from one another at a larger bottom(operatively anterior) surface 798. It is noted that also according tothe invention the surface 796 may be placed in an anterior position andthe surface 798 placed in a posterior position with respect to the spineif desired to correct spinal kyphosis. In other embodiments of theinvention the core 706 and spacer 710 may be bent, sized and shaped forthe correction of other spinal deformities, such as scoliosis, forexample.

The assembly 701 is assembled in a manner substantially similar to themanner of assembly previously described herein with respect to theassembly 501. Therefore, the core 706 is first received within a throughbore of the spacer 710 formed by the surfaces 784, then within the innerplanar surfaces 764 and 766 of the sleeve 712, followed by an innerthrough bore of the bumper 718 and then an inner through bore of thecrimping member 720. Similar to what has been described previously withrespect to the assembly 1, the core 706 is initially of a longer lengthmeasured along the axis BB than is shown in the drawing figures,allowing for a manipulation tool to grasp the core 706 near an endthereof that extends through the crimping member bore. The core 706 istensioned and/or the spacer 710 and bumper 720 are compressed, followedby deformation of the crimping member 720 against the core 706. The core706 is then trimmed substantially flush to the crimping member 720. Theassembly is now in dynamic relationship with the core 706 being intension while the spacer 710 that is slidable with respect to the core706 is compressed between the plates 746 and 770 and the bumper 718 thatis also slidable with respect to the core 706 is compressed between thesleeve 712 and the crimping member 720; the spacer 710 and the bumper718 placing a distractive force on the core 706 along the axis BB andbetween the buttress plate 746 and the crimping member 720. The assembly701 may then be implanted, cooperating with a pair of bone screws 525 asillustrated in FIG. 43 and as previously described herein with respectto the assembly 501. Unlike the assembly 501 illustrated in FIG. 38 thebent core 706 and cooperating trapezoidal spacer 710 provide additionalsupport or correction to a spine, for example, when correcting spinallordosis. With reference to FIG. 44, the assembly 701 and cooperatingbone screws 525 of FIG. 43 are shown under a load that causes the core706 to straighten and further compresses the spacer 710 resulting in abulging of the flexible spacer at the anterior surface 798.

With reference to FIGS. 45-49, another embodiment of a dynamiclongitudinal connecting member assembly, generally 801 is illustrated.The assembly 801 includes an anchor member 804 having an inner core 806and a bone anchor attachment portion 808; a trapezoidal spacer 810, asleeve 812, a second spacer 814, a second sleeve 816, a bumper 818 and acrimping member 820. The illustrated spacer 810, sleeve 812, bumper 818and crimping member 820 are identical or substantially similar to therespective spacer 710, sleeve 712, bumper 718 and crimping member 720previously described herein with respect to the assembly 701. The anchormember 804 is identical to the anchor member 704 with the exception thatthe bone anchor attachment portion 808 is of a greater length to receivethree bone screw receivers 531 therealong while the portion 708 is sizedto receive two bone screw receivers 531. The second spacer 814 issubstantially similar in shape and function as the spacer 510 previouslydescribed herein with respect to the assembly 501 with the exceptionthat the through bore defined by the inner planar surfaces is uniform(see FIG. 46) and does not require a flared portion for cooperating withthe core 806 as the spacer 814 is disposed along a uniform mid-sectionof the core 806.

The sleeve 816 is for the most part similar to the sleeve 812, thesleeve 712 and the sleeve 512 of the previously described embodiments,having outer planar surfaces 860 and 862, a rectangular cross-section,inner planar surfaces 864 and 866 defining a through bore for closelyreceiving the core 806 and an end plate 870 identical or substantiallysimilar to the respective outer surfaces 560 and 562, inner surfaces 564and 566 and end plate 570 of the sleeve 512 previously described hereinwith respect to the assembly 501. Additionally, the sleeve 816 has anopposite end plate 871 spaced from and parallel to the end plate 870.

The assembly 801 is assembled in a manner substantially similar to themanner of assembly previously described herein with respect to theassembly 701. The core 806 is first received within a through bore ofthe spacer 810, then within the inner planar surfaces 864 and 866 of thesleeve 816, followed by an inner through bore of the spacer 814 and thena through bore of the sleeve 812. Thereafter, the core 806 is receivedin an inner through bore of the bumper 818 and then an inner throughbore of the crimping member 820. Similar to what has been describedpreviously with respect to the assemblies 501 and 701, the core 806 isinitially of a longer length than is shown in the drawing figures,allowing for a manipulation tool to grasp the core near an end thereofthat extends through the crimping member bore. The core 806 is tensionedand/or the spacers 810 and 816 and the bumper 818 are compressed,followed by deformation of the crimping member 820 against the core 806.The core 806 is then trimmed substantially flush to the crimping member820. The assembly is now in dynamic relationship with the core 806 beingin tension while the spacers 810 and 816 that are slidable with respectto the core 806 are compressed and the bumper 818 that is also slidablewith respect to the core 806 is compressed between the sleeve 812 andthe crimping member 820; the spacers 810 and 816 and the bumper 818placing a distractive force on the core 806 along an elongate axisthereof. The assembly 801 may then be implanted, cooperating with athree bone screws 525 as illustrated in FIG. 48 and as previouslydescribed herein with respect to the assembly 501. Unlike the assembly501 illustrated in FIG. 38 the bent core 806 and cooperating trapezoidalspacer 810 provide additional support or correction to a spine, forexample, when correcting spinal lordosis. With reference to FIG. 49, theassembly 801 and cooperating bone screws 525 of FIG. 48 are shown undera load that causes the core 806 to straighten and further compresses thespacer 810 resulting in a bulging of an anterior surface of the spacer810.

It is foreseen that longitudinal connecting member assemblies accordingto the invention may be of a variety of lengths for cooperation with aplurality of bone screws 525, either along an attachment portion, suchas the portion 808 or along dynamic portions that include one or morespacers and one or more sleeves, such as the sleeves 512, 712, 812 and816 for attachment of a plurality of bone screws 525 or other boneanchors. It is foreseen that such sleeves may also be a variety oflengths for attachment to one or more bone anchors along a length of theindividual sleeve.

As another example of an elongate dynamic connecting member of theinvention for use with at least three bone screws 525, FIGS. 50-52illustrate another embodiment of a dynamic longitudinal connectingmember assembly, generally 901. The assembly 901 includes an anchormember 904 having an inner core 906 and a bone anchor attachment portion908; first and second trapezoidal spacers 910A and 910B, a sleeve 912, asecond sleeve 916, a bumper 918 and a crimping member 920. Theillustrated trapezoidal spacers 910A and 910B are identical orsubstantially similar to the trapezoidal spacer 710 previously describedherein with respect to the assembly 701. The second spacer 910B wouldnot require an inner flared portion as such spacer is placed along auniform mid-section of the core 906. The sleeves 912 and 916 aresubstantially similar to the respective sleeves 812 and 816 previouslydescribed herein with respect to the assembly 801. The bumper 918 andcrimping member 920 are identical or substantially similar to therespective bumpers 518, 718 and 818 and crimping members 520, 720 and820 previously described herein with respect to the assemblies, 501, 701and 801. The anchor member 904 is identical to the anchor member 804with the exception that the core 906 is bent at two locationscorresponding to the operative placement of the trapezoidal spacers 910Aand 910B.

The assembly 901 is assembled in a manner substantially similar to themanner of assembly previously described herein with respect to theassembly 801. The core 906 is first received within a through bore ofthe spacer 910, then within the inner planar surfaces defining the innerthrough bore of the sleeve 916, followed by an inner through bore of thespacer 910A and then a through bore of the sleeve 912. Thereafter, thecore 906 is received in an inner through bore of the bumper 918 and thenan inner through bore of the crimping member 920. Similar to what hasbeen described previously with respect to the assemblies 501, 701 and801, the core 906 is initially of a longer length than is shown in thedrawing figures, allowing for a manipulation tool to grasp the core 906near an end thereof that extends through the crimping member bore. Thecore 906 is tensioned and/or the spacers 910A and 910B and the bumper918 are compressed, followed by deformation of the crimping member 920against the core 906. The core 906 is then trimmed substantially flushto the crimping member 920. The assembly is now in dynamic relationshipwith the core 906 being in tension while the spacers 910A and 910B thatare slidable with respect to the core 906 are compressed and the bumper918 that is also slidable with respect to the core 906 is compressedbetween the sleeve 912 and the crimping member 920; the spacers 910A and910B and the bumper 918 placing a distractive force on the core 946along an elongate axis thereof. The assembly 901 may then be implanted,cooperating with a three bone screws 525 as illustrated in FIG. 51 andas previously described herein with respect to the assembly 501. Similarto the assembly 801, the bent core 906 and cooperating trapezoidalspacers 910A and 910B provide additional support or correction to aspine, for example, when correcting spinal lordosis. With reference toFIG. 52, the assembly 901 and cooperating bone screws 525 of FIG. 51 areshown under a load that causes the core 906 to straighten and furthercompresses the spacers 910A and 910B resulting in a bulging of anteriorsurfaces of the spacers 910A and 910B.

It is to be understood that while certain forms of the present inventionhave been illustrated and described herein, it is not to be limited tothe specific forms or arrangement of parts described and shown.

1. In a medical implant assembly having at least first and second boneanchor attachment structures cooperating with a longitudinal connectingmember, the improvement wherein the longitudinal connecting membercomprises: a) an anchor member portion in engagement with the first ofthe bone anchor attachment structures having a longitudinal axis, theanchor member portion having an extension of reduced diameter extendingfrom an end thereof, the extension is initially tensioned along thelongitudinal axis and thereafter can be further tensioned when theassembly is fully assembled by releasing a stiff end structure; b) acompressible outer spacer, the extension being received in the spacer,the spacer being positioned between the first and second bone anchorattachment structures and held in compression by the extension; and c) asleeve, the extension being received within the sleeve and in slidablerelationship therewith, the sleeve being in engagement with a second ofthe bone anchor attachment structures.
 2. The improvement of claim 1further comprising an elastic bumper, the extension being receivedwithin the bumper and the bumper engaging the sleeve.
 3. The improvementof claim 1 wherein the extension is fixed to the anchor member portionat an end thereof.
 4. In a medical implant assembly having at leastfirst and second bone attachment structures cooperating with alongitudinal connecting member, the improvement wherein the longitudinalconnecting member comprises: a) a rigid anchor member portion with afirst diameter in engagement with the first of the bone anchorattachment structures, the anchor member portion having a longitudinalaxis; b) an attached flexible core extension member with a secondreduced diameter along a length thereof, the core extension memberconnected to and extending from the anchor member portion and being intension and thereafter can be further tensioned when the assembly isfully assembled by releasing a stiff end structure; c) a compressibleouter spacer, the core extension member being received in the spacer,the spacer being positioned between the first and second bone attachmentstructures; and d) a sleeve, the core extension member being receivedwithin the sleeve and in slidable relationship therewith, the sleevebeing secured to the second of the bone attachment structures.
 5. In amedical implant assembly having at least first and second bone anchorattachment structures cooperating with a longitudinal connecting member,the improvement wherein the longitudinal connecting member comprises: a)a rigid anchor member portion with a first diameter in engagement with afirst of the bone anchor attachment structures, the anchor memberportion having a longitudinal axis; b) a flexible extension member witha second reduced diameter extending from an end thereof, the extensionmember attached to and extending from the anchor member portion and isinitially tensioned along the longitudinal axis to a steady state lengthand thereafter can be further tensioned when the assembly is fullyassembled by releasing a stiff end structure; c) a compressible outerspacer, the extension member being received in the spacer, the spacerbeing positioned between the at least two bone anchor attachmentstructures; and d) a sleeve, the extension member being received withinthe sleeve and in slidable relationship therewith, the sleeve being inengagement with the second of the bone anchor attachment structures. 6.The improvement of claim 5, further comprising an elastic bumper, theextension member being received within the bumper and the bumperengaging the sleeve.
 7. The improvement of claim 5, further comprising afixation structure secured to the extension member at an end thereofopposite the anchor member portion.
 8. The improvement of claim 5,wherein the extension member is fixed to the anchor member portion at anend thereof.
 9. In a medical implant assembly having at least first andsecond bone attachment structures cooperating with a longitudinalconnecting member, the improvement wherein the longitudinal connectingmember comprises: a) a rigid anchor member portion with a first diameterin engagement with the first of the bone attachment structures, theanchor member portion having a longitudinal axis; b) a bendable coreextension member with a second reduced diameter along a length thereof,the core extension attached to and extending from the anchor memberportion, the extension having a linear and a non-linear configurationand is initially tensioned along the longitudinal axis to a steady statelength and thereafter can be further tensioned when the assembly isfully assembled by releasing a stiff end structure; c) a compressibleouter spacer, the core extension member being received in the spacer,the spacer being positioned between the first and second bone attachmentstructures; and d) a sleeve, the core extension member being receivedwithin the sleeve and in slidable relationship therewith, the sleevebeing in engagement with the second of the bone attachment structures.10. A medical implant assembly with at least first and second boneattachment structures including: a) a longitudinal connecting memberhaving a stiff portion with a first diameter secured to at least thefirst bone attachment structure having a longitudinal axis, the stiffportion being coaxial with a less stiff core extension portion with asecond diameter of reduced width relative to the stiff portion firstdiameter, the core extension portion being in slidable relation with thesecond bone attachment structure, and is initially tensioned along thelongitudinal axis to a steady state length and thereafter can be furthertensioned when the assembly is fully assembled by releasing a stiff endstructure; b) a solid non-slitted outer spacer positioned entirelyoutside of the core extension portion and between the first and secondbone attachment structures, the spacer being in slidable relation withthe core extension portion; and c) an end fixing structure and anelastic bumper, both the wherein at least one sleeve is positionedaround and between the end fixing structure and the elastic bumper beingpositioned entirely outside of the second bone attachment structure,wherein the bumper is positioned around the core extension portion andbetween the fixing structure and the second bone attachment structure,and wherein the bumper is in slidable relation with the core extensionportion; and wherein d) the fixing structure is slidable on the coresection, compressible against the bumper and securable to the coreextension portion.
 11. The assembly according to claim 10, wherein thecore extension portion is maintained in tension by axial elasticdistraction from the bumper.
 12. The assembly according to claim 10,wherein the core extension portion is made of at least one of a polymer,PEEK and a non-metal.
 13. The assembly according to claim 10, coreextension portion and the bone attachment structure, the sleeve beingsecured to at least the bone attachment structure.
 14. The assemblyaccording to claim 10, wherein the tensioned core extension portion isadapted to provide resilient bending stiffness for the longitudinalconnecting member while cooperating with the bone attachment structures.15. The according to claim 10, wherein the end fixing structure ispositioned entirely outside of the bumper.
 16. The assembly according toclaim 10, wherein the bumper and the spacer are positioned entirelyoutside of the sleeve.
 17. A longitudinal connecting member adapted foruse in joining first and second bore attachment structures comprising:a) an anchor member having a first rigid portion with a first diameterand being adapted for joining to the first bone attachment structure; b)a flexible core extension member having a longitudinal axis andextending outward from the first portion and being initially tensionedalong the longitudinal axis to a steady state length and thereafter canbe further tensioned when the assembly is fully assembled by releasing astiff end structure; c) a sleeve adapted to be joined to the second boneattachment structure and having a bore; the core extension member beingslidably received in the bore and the sleeve being maintained on theextension member.
 18. The connecting member according to claim 17,wherein the anchor member first portion and core extension member arescrewably joined so as to be fixed together.
 19. The connecting memberaccording to claim 17, wherein the anchor member first portion and coreextension member are constructed of dissimilar materials.
 20. Theconnecting member according to claim 17, including a compressibly spacerslidably received on the core extension member between the anchor memberfirst portion and the sleeve.
 21. The connecting member according toclaim 20, including an end fixing structure secured to an end of thecore extension member opposite the first portion and abutting againstthe sleeve on a side opposite the first portion.
 22. The connectingmember according to claim 17, wherein the anchor member first portionand core extension member are fixedly secured to each other.
 23. Amedical implant assembly having at least two bone attachment structurescooperating with a longitudinal connecting member, wherein thelongitudinal connecting member includes: a) a rigid anchor memberportion with a first diameter in engagement with one of the at, leasttwo bone attachment structures; b) a pre-tensioned flexible inner coreextension member with a second reduced diameter, the flexible coreextension member extending longitudinally from the anchor member portionalong a substantially central axis of the longitudinal connectingmember, the flexible core extension member being formed of apolyethylene polymer; c) at least one compressible outer spacer with apair of opposed end surfaces and having a first through bore, and beingformed of a urethane polymer, the flexible core extension member beingreceived in the first through bore of the spacer, the spacer beingpositioned between the at least two bone attachment structures; d) atleast one sleeve having a second through bore, the sleeve being formedof a non-metallic polymer, the flexible core extension member beingreceived within the second through bore of the sleeve and in slidablerelationship therewith, the sleeve being in engagement with the other ofthe at least two bone attachment structures; e) an elastic bumper formedof an elastomer, the flexible core extension member being receivedwithin the bumper and the bumper engaging the sleeve f) a rigid endblocker fixed to the flexible core extension member at an end thereofopposite the anchor member portion, the rigid end blocker beingaccessible outside the bone attachment structures so that the cord andthe assembly may be further tensioned.